On 07.06.2012, at 14:13, David Gibson wrote: > On Thu, Jun 07, 2012 at 01:27:56PM +0200, Alexander Graf wrote: >> >> On 07.06.2012, at 01:45, David Gibson wrote: >> >>> [snip] >>>>> You mean internally? Yeah, probably. Externally? The point of these >>>>> helpers is to make the code look less cluttered. We can already pass in >>>>> an array just fine, but C is quite annoying about generating those on >>>>> the fly, while it's easy to pass in ints as parameters :) >>>> >>>> Varargs? >>> >>> Ugly and risky with standard C varargs (because an explicit length >>> would be needed). Could be done neatly with gcc macro varargs. >> >> Could a combination of both like this work? >> >> #include <stdio.h> >> #include <stdarg.h> >> >> #define __VA_NARG__(...) \ >> (__VA_NARG_(_0, ## __VA_ARGS__, __RSEQ_N()) - 1) >> #define __VA_NARG_(...) \ >> __VA_ARG_N(__VA_ARGS__) >> #define __VA_ARG_N( \ >> _1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \ >> _11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \ >> _21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \ >> _31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \ >> _41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \ >> _51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \ >> _61,_62,_63,N,...) N >> #define __RSEQ_N() \ >> 63, 62, 61, 60, \ >> 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, \ >> 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, \ >> 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, \ >> 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, \ >> 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, \ >> 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 >> >> #define PRINT_ELEMS(fdt, ...) print_elems(fdt, __VA_NARG__(__VA_ARGS__), >> __VA_ARGS__) > > Um.. that might work, but it's ludicrously complicated. If we're > prepared to use the gcc statement expression extension and we're just > going to abort on errors like findnode_nofail, it can be done much > more easily using c99 variadic macros: > > #define setprop_ints(fdt, path, prop, ...) \ > do { \ > uint32_t tmp[] = {__VA_ARGS__}; \ > > if (fdt_setprop(findnode_nofail(fdt, path), prop, \ > tmp, sizeof(tmp)) != 0) { \ > /* error message */ \ > abort(); \ > } \ > } while (0)
Hrm. But here we'd be overloading the name space, no? If anyone passes in tmp[3] as parameter to setprop_ints, it would conflict with the internal variable tmp, right? Alex